Process for producing thioethers



United States Patent O" 0,573 7 Claims. or. 260-609) This inventionrelates to a process for producing thioethers and, more particularly, tothe production of alkyl thioethers, i.e., straight-chain or brancheddialkyl monosulphides, of the general formula RSR', in which the alkylgroups R and R may be similar or different, a specific example of whichis ethyl sulphide.

Thioethers can be produced by various well-known methods, particularlyby the condensation of olefines with hydrogen sulphide. The techniqueswhich have been used in this type of reaction utilize the property ofthe olefines' of combining with the H 5, in the presence of variouscatalysts, to give mercaptans and alkyl sulphides. In thesepreviously-known processes, the reaction generally takes place in thegaseous phase, at a temperature from 200 to 300 C.; however, it has beenfound that the conversion rates are not very high, particularly in thecase of ethylene. Another disadvantage of the prior art is that thesulphidts which are formed are absorbed by the catalyst and inhibit theaction of the latter. While it is true that raising the temperatureassists the desorption, it has the effect of displacing the equilibriumin the inverse sense. In the most favorable cases, the alkyl suphideobtained is always contaminated with mercaptans. It is also necessarywith the known processes to have rather pure reagents in order to avoidthe dangers of the catalyst becoming poisoned.

It is, therefore, an outstanding object of the invention to provide aprocess for the production of thioethers in which the rate of conversionis higher than with previously-known processes.

Another'object of this invention is the provision of a process for theproduction of thioethers in which hydrogen sulphide may be used in animpure form, such as industrial gas originating in refineries or innatural gas wells, without affecting the product.

A further object of the present invention is the provision of a processfor producing thioethers wherein it is possible to employ a gas whichcontains large proportions of CO without affecting the conversion rateor the purity of the product obtained.

It is another object of the instant invention to provide a process forproducing thioethers in which the sulphides are not absorbed by thecatalyst and, therefore, do not inhibit the latter.

It is a further object of the invention to provide a process forproducing thioethers in which the product is not contaminated withmercaptans.

With the foregoing and other objects in view, which will appear as thedescription proceeds, the invention resides in the combination andarrangement of steps and in the details of operation hereinafterdescribed and claimed, it being understood that changes in the preciseembodiment of the invention herein disclosed may be made within thescope of what is claimed without departing from the spirit of theinvention.

In general, the process of the invention consists in causing one or moreolefines to react with hydrogen sulphide 3,333,008 Patented July 25,1967 in the liquid phase in the presence of sulphur and a catalystselected from known vulcanization agents. The operation takes placeunder a pressure sufiicient for the reaction medium to remain liquid.

Another feature of the invention is that the reactional liquid phasecontains a solvent of the thioether (or thioethers) which is to beprepared; it is preferable for the solvent being used to, have a goodionizing power. In one particularly advantageous embodiment, thissolvent is formed by a certain quantity of the thioether itself.

Among the vulcanization agents capable of being used as a catalyst in aprocess carried out in accordance with the teachings of the invention,are the mercaptorbenzthiazole derivatives, such as mercaptobenzthiazole,mercaptobenzthiazole disulphide,N-cyclohexyl-Z-benzthiazolesulphenamide, 2-morpholinodithiobenzthiazole,2- morpholinothiobenzthiazole, 1,3 bis-(2-benzthiazoyl)- thiomethylurea,2-(2,4-dinitrophenylthio)-benzthiazole, 2-benzthiazolyl-N,N'-diethylthiocarbamyl sulphide. Vulcanization agents ofthe dithiocarbamates and thiuram types can be used, examples of thesebeing zinc dimethylthiocarbamate, tetramethylthiuram disulphide, andtetramethylthiuram sulphide. Derivatives of guanidine can also be used,such as diphenylguanidine and 1,3-di-o-tolylguanidine. Schiifs bases,i.e., aldehyde and amine combinations, are likewise suitable; it is, forexample, possible to employ a mixture of butyraldehyde with aniline.Another series of vulcanization agents which can be used comprises thethio-bis-amines, particularly dithio-bis-diethylamine, 'dimethylamine,diisopropylamine, dioc'tylamine, di-B-ethylaminopropionitrile,dicyclohexylaminoacetonit-rile, dipyrrolidine, dipiperidine, andN-dimorpholine. Amines, such as triethylamine, trimethylamine, anddiaminodiphenylmethane, are also suitable for catalyzing the reaction inaccordance with the invention. The catalysts can also be provided fromthe different thiocompounds, such as xanthates and derivatives ofthiourea, for example, ethylene thioure'a.

Although catalysts having various boiling points may be employed, it ispreferable in each case to select a catalyst whose boiling point isconsiderably different from that of the thioether to be manufactured; inthis way, it is easier for the product which is produced to be separatedfrom the catalyst. The invention permits a very wide choice ofcatalysts, so that it is possible to use the conditions which are mostadvantageous in each particular case. For example, in the manufacture ofethyl sulphide, which boils at 92 C., it is well to employ catalystsboiling at a distinctly higher temperature, such as the aforementionedmercaptobenzthiazoles.

The proportions of catalyst to be employed can also vary within fairlylarge limits, the proportions by weight depending to some extent on themolecular weight of the catalyst chosen. In general terms, the catalystconcentration in the reaction medium may be of the order of 2% to 30% byweight, and preferably in the range from 5% to 15%; proportions ofcatalyst in the region of 10% give excellent results when starting withlight olefins, such as ethylene, propylene, and butene.

The liquid phase, made up of the reaction medium, must be strictlymaintained under a more or less high pressure when the olefin being usedboils at a tempera ture lower than that at which the reaction takesplace, i.e., generally between C. and 200 0; since, at the same time, acertain pressure is also required for maintaining the hydrogen sulphidein the reaction medium at this temperature, the inventive process isgenerally used under pressures which are higher than atmospheres,although this does not necessarily rule out the possibility of workingunder lower pressures. In the most usual forms of the invention, thepressure is of the order of 10 atmospheres to 300 atmospheres, thesevalues not being in any way limitative. The pressure limits are afunction of the composition and the nature of the mixture of compoundsat the reaction temperature; the influence of the pressure is of twotypes: on the one hand, it increases the speed of the reaction and, onthe other hand, it permits operation in a liquid phase of desiredcomposition.

Although the temperature of the reaction, in the new process, isgenerally between 100 and 200 C., it may in certain cases exceed theselimits; when it is a question of producing thioethers from lightolefins, the preferred temperature range is from 130 to 170 C.

According to another feature of the invention, the preparation iseffected in the presence of an excess of hydrogen sulphide. It isinteresting to note that this excess, which improves the conversion rateof the olefin, does not in any way modify the selectivity of the veryspecific reaction of the thioethers.

The manufacture, in accordance with the invention, can be carried out inany known apparatus.

In order to illustrate the invention, a few nonlimitative examples aregiven below.

Example I Example II 10 g. of sulphur, 200 ml. of ethyl sulphidecontaining 13 g. of trimethylamine and 270 g. of H S were introducedinto an autoclave; the mixture was heated to 140, ethylene was injectedat a pressure of 100 atmospheres and this pressure was maintained for 3hours. Under these conditions, 800 ml. of ethyl sulphide were obtained.

Example III Under the same conditions as in Example I, a mixture of 20g. of zinc dimethylthiocarbamate, 15 g. of benzoic acid, and 7.5 g. ofsulphur was introduced as a catalyst. After operating for 6 hours, thesame quantities of ethyl sulphide as in Example I were obtained.

Example IV Under the same conditions as in Example II, g. ofdithio-bis-diethylamine in solution in 200 ml. of ethyl sulphide and 5g. of sulphur were used as catalyst. The results were identical withthose of Example II.

Example V The steps of Example I were repeated, except that the additionof 7.5 g. of sulphur was omitted; that is to say, mercaptobenzothiazolwas used alone as a catalyst. N0 ethyl sulphide was obtained.

Example VI The steps of Example I were repeated, except that nomercaptobenzothiazol was introduced into the reaction nixture. Only 65g. of ethyl sulphide were obtained.

Example VII The general steps of Example I were repeated, but ieithersulphur nor mercaptobenzothiazol were added to he reaction mixture.There was no formation of ethyl :ulphide at all.

4 Example VIII The following mixture was introduced into a reactor ofstainless steel:

Butyraldehyde 18 Anilin 23.5 Sulphur 7.5

After the reactor had been closed, 400 g. of H S were injected thereinand then, 840 g. of propylene were care Example IX The following wereintroduced into an autoclave of stainless steel: 832 g. of styrene, 10g. of di-ortho-toly1- guanidin, 5 g. of sulphur, 340 g. of H 8. Themixture was heated for 3 hours at about 140-150 C. The autoclave wasthen cooled, and 890 g. of diphenylethylsulphide were obtained, theboiling point of which, under 0.2 mm. Hg, is 117-135 C.; the refractionindex, n of the compound is 1.5823.

Example X The steps of Example I were repeated, except that thetemperature was 120 C. After 4 hours of heating, only 235 g. of ethylsulphide were obtained.

Example XI The steps were similar to those carried out in Example I, butthe temperature was raised to 180 C. the reaction became very violent.It was stopped by rapidly cooling the reactor, and after re-heating toC., it went on with a great difiiculty, probably duevto the destructionof the catalyst. 370 g. of ethyl sulphide were obtained.

While it will be apparent that the illustrated embodiments of theinvention herein disclosed are well calculated adequately to fulfill theobjects and advantages pri marily stated, it is to be understood thatthe invention is susceptible to variation, modification, and changewithin the spirit of the subjoined claims.

The invention having been thus described, what is claimed as new anddesired to secure by letters Patent is:

1. A proces for producing thioethers by the condensation of hydrogensulphide with a substance selected from the class consisting ofethylene, propylene, and butene, consisting of the step of heating thehydrogen sulphide and the substance in the liquid state in the presenceof a catalytic system made up of sulfur and a rubber vulcanization agentselected from the class consisting of mercaptobenzthiazoles,dithiocarbamates, thiurams, Schiifs bases, guanidines, thio-bis-amines,amines, xanthates, and thioureas.

2. A process as recited in claim 1, wherein the lastnamed class alsoincludes dimethylamine, dimethylthiocarbamate salts, dithio-bisdiethylamine, aniline, and diortho-tolyl guanidine.

3. A process as recited in claim 1, wherein the heating takes place at atemperature in the range from 100 to 200 C. under a pressure which issufiicient to maintain the reaction medium in the liquid state.

4. A process as recited in claim 1, wherein the proportion of each ofthe constituents of the catalytic system is in the range from 1% to 20%tion medium.

5. A process as recited in claim 1, wherein the reaction mediumcomprises a solvent of hydrogen sulfide, the

75 first-named substance, and the second-named substance.

of the weight of the reac- 5 6 6 A process as recited in claim 5,wherein the solvent about 140 C. and its pressure at about 100 atmosisthe th'ioether which is to be produced. pheres, and

7. A process for producing ethyl sulfide, comprising ((1) separatingethyl sulphide from the resulting product the steps of: by distillation.

(a) forming a mixure of sulphur, hydrogen sulphide, 5 References Citedand a vulcanization agent selected from the class con- Naylor Journal ofPolymer Science Vol. pp

sisting of mercaptobenzthiazoles, dithiocarbarnates, 307 (1946)thiurams, Schiffs bases, 'guanidines, thio-bis-amines, amines,xanthates, thioureas, and their derivatives, CHARLES R PARKER, PrimaryExaminer.

(b) introducing ethylene into the mixture, 10 (c) maintaining thetemperature of the mixture at DIILBERT PH1LLIPS,ASSlSmm Examine!-

1. A PROCESS FOR PRODUCING THIOETHERS BY THE CONDENSATION OF HYDROGEN SULPHIDE WITH A SUBSTANCE SELECTED FROM THE CLASS CONSISTING OF ETHYLENE, PROPYLENE, AND BUTENE, CONSISTING OF THE STEP OF HEATING THE HYDROGEN SULPHIDE AND THE SUBSTANCE IN THE LIQUID STATE IN THE PRESENCE OF A CATALYTIC SYSTEM MADE UP OF SULFUR AND A RUBBER VULCANIZATION AGENT SELECTED FROM THE CLASS CONSISTING OF MERCAPTOBENZTHIAZOLES, DITHIOCARBAMATES, THIURAMS, SCHIFF''S BASES, GUANIDIENES, THIO-BIS-AMINES, AMINES, XANTHATES, AND THIOUREAS. 